A hand-held computing device—such as, for example, a cell phone, a smart phone, a mobile internet device, etc.—typically includes several components disposed on a system-level circuit board. The aforementioned components may include integrated circuit (IC) devices, passive electrical components, and various input/output (I/O) devices, as well as any combination of these and/or other components. Many of these components—although perhaps not all—may be assembled onto the system-level board, which may be referred to as a mainboard. The mainboard provides electrical paths to interconnect these various components to form a computing system.
For hand-held computing devices, a system-level board assembly having a small form factor may be desirable. One solution to achieve a small form factor is to use a package-on-package (PoP) architecture, which generally includes an upper IC package stacked over and electrically coupled with a lower IC package, each package including one or more IC die disposed on a substrate or other die carrier. However, a PoP component may increase the overall height (or thickness) of the assembly. Further, the relatively lower layer count commonly found in the lower substrate of a PoP component (e.g., 2-4 layers, as compared to the mainboard, which may have 6 or more layers) can limit routing flexibility between the upper and lower packages. Conversely, to mount these two packages side-by-side on the mainboard will increase the surface area of the assembly.